Molar Pregnancy

A molar pregnancy mimic a healthy pregnancy.

A molar pregnancy is an abnormality of the placenta, caused by a problem when the egg and sperm join together at fertilization. Molar pregnancies are rare, occurring in 1 out of every 1,000 pregnancies. Molar pregnancies are also called gestational trophoblastic disease (GTD), hydatidiform mole or simply referred to as a “mole.”

What is a molar pregnancy?

A molar pregnancy is the result of a genetic error during the fertilization process that leads to growth of abnormal tissue within the uterus. Molar pregnancies rarely involve a developing embryo, and the growth of this material is rapid compared to normal fetal growth. It has the appearance of a large and random collection of grape-like cell clusters. There are two types of molar pregnancies, “complete,” and “partial.”

What is a complete molar pregnancy?

Complete molar pregnancies have only placental parts (there is no baby), and form when the sperm fertilizes an empty egg. Because the egg is empty, no baby is formed. The placenta grows and produces the pregnancy hormone, hCG. Unfortunately, an ultrasound will show that there is no fetus, only a placenta.

What is a partial molar pregnancy?

  • Partial Mole occurs when the mass contains both the abnormal cells and an embryo that has severe defects. In this case the fetus will be overcome by the growing abnormal mass rather quickly.
  • An extremely rare version of a partial mole is when twins are conceived but one embryo begins to develop normally while the other is a mole. In these cases, the healthy embryo will very quickly be consumed by the abnormal growth.

Who is at risk for a molar pregnancy?

  • In the US, approximately 1 out of 1,000 pregnancies is a molar pregnancy
  • Mexico, Southeast Asia, and the Philippines have higher rates than the US for molar pregnancies in women
  • White women in the US are at higher risk than black women
  • Women over the age of 40
  • Women who have had a prior molar pregnancy
  • Women with a history of miscarriage

What are the symptoms of a molar pregnancy?

How do I know if I have a molar pregnancy?

  • A pelvic exam may reveal a larger or smaller uterus, enlarged ovaries, and abnormally high amounts of the pregnancy hormone hCG.
  • A sonogram will often show a “cluster of grapes” appearance, signifying an abnormal placenta.

How is a molar pregnancy treated?

  • Most molar pregnancies will spontaneously end and the expelled tissue will appear grape-like.
  • Molar pregnancies are removed by suction curettage, dilation and evacuation (D & C), or sometimes through medication. General anesthetic is normally used during these procedures.
  • Approximately 90% of women who have a mole removed require no further treatment.
  • Follow-up procedures that monitor the hCG levels can occur monthly for six months or as your physician prescribes.
  • Follow-up is done to ensure that the mole has been removed completely. Traces of the mole can begin to grow again and may possess a cancerous-type threat to other parts of the body.
  • Pregnancy should be avoided for one year after a molar pregnancy.
  • Any birth control method is acceptable with the exception of an intrauterine device.

How will I feel emotionally after a molar pregnancy?

Although the removal of a molar pregnancy is not the termination of a developing child, it is still a loss. Even when an embryo is present, it does not have the opportunity to develop into a child. Most women discover that they are dealing with a molar pregnancy after the discovery and anticipation of being pregnant. Dreams, plans and hopes are cancelled all at once; it is still a significant loss.

  • There will have to be healing time for all involved, and grief will be experienced.
  • Recognize that people may try to console you with statements like, “Well at least it wasn’t a baby.” This doesn’t help, but at least know that they are trying. Let them know what you need.
  • What makes this type of loss further different from a “normal miscarriage” or loss is the continued concern of the mother’s health. Make sure that you stick with your follow-up appointments.
  • Support groups and counseling may prove beneficial.

Can I have another molar pregnancy?

  • If you had a molar pregnancy without complications, your risk of having another molar pregnancy is about 1-2%.
  • Genetic counseling prior to conceiving again is helpful for some couples.
Last Updated: 03/2006

Compiled using information from the following sources:

MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); [updated 2006 Feb 21]. Pregnancy Loss; [updated 2006 Feb 22; reviewed 2006 Feb 7; cited 2006 Feb 22]. Available from: http://www.nlm.nih.gov/medlineplus/pregnancyloss.html

Current Obstetric & Gynecologic Diagnosis & Treatment-Ninth Ed. DeCherney, Alan H., et al, Ch. 50.